BachNagel » Contentment »
Nearly 40 percent of final energy consumption in Germany is accounted for by the building sector
Optimized energy balance
The window: The great energy saving potential
The era of cheap and abundant fossil energy is long over. Our most important energy source, crude oil, according to forecasts, will only last about 40 years. Not least for this reason, the price of heating oil has tripled in the last 10 years and is expected to double again by 2030. There is still great potential for savings in private households. The building sector accounts for almost 40 percent of final energy consumption in Germany.
In private households, heating and hot water preparation alone require 85 percent of the energy, a further 15 % is required for electricity (including cooling units).
Anyone who does not want to permanently spend an ever-increasing part of their wages on heating must consistently reduce their energy consumption.
It is worthwhile itself very much with the advantages of the correct combination of window, roll shop and sun protection to argue.
The ESCORP-EU25 study proves that a holistic approach is needed.
The right combination of windows, roller shutters and sun protection offers maximum thermal and visual comfort.
The decisive factor is:
- To provide the most effective protection against the cold in winter and to use the free solar energy
- fend off the heat in summer and ensure sufficient light without glare
The external protection is the most effective of all measures and the roller shutter is the big winner.
From outside – The roller shutter prevents the wind from cooling down the static layer of air between the roller shutter and the window.
From the inside – As a result, the window is less cooled and the energy transmission from the inside to the outside is greatly reduced, because warm air flows, according to the principle of thermodynamic equilibrium, to bodies with lower temperatures until the temperatures have adjusted to each other.
In addition, the roller shutter acts as a protective shield against heat radiation.
Investigations by the Fraunhofer Institute for Building Physics have shown that the installation of a standard front-mounted roller shutter with double glazing resulted in an increase in surface temperature on the outside of the glazing of about 3°. The difference to the room temperature is reduced.
Internal protection lacks the advantages of roller shutters and is therefore less effective. An internal protection also prevents heat radiation from reaching the window, which is unprotected from the outside and therefore colder. The window remains cold and condensation and the consequences quickly develop.
The Physibel study by a European umbrella organisation confirms that roller shutters reduce the heating energy requirement by approx. 10% and that window protection systems with high air permeability cannot deliver this performance.
From practice one knows that the saving potential by roll shops with older windows lies with up to 54%.
Further investigations by the Fraunhofer Institute for Building Physics have shown that a closed roller shutter also improves the thermal insulation of a modern, heat-insulating glazed window in winter conditions by 27 %.
No other protection achieves this high level of thermal insulation
A window with a thermal insulation glazing with a U-value of 1.1 W/m².K becomes a window with a thermal insulation glazing with a U-value of 0.8 W/m².K using a roller shutter.
The U-value (thermal insulation value) indicates how much energy flows out per degree of temperature difference over an area of 1 m² of building envelope.
The U-value is given in watts per square meter times Kelvin=W/m²K.
Save money in winter with automated roller shutters
To achieve maximum energy savings, automated control with sun and temperature sensors makes sense. In good weather the shutters are opened early and the solar energy is used to heat the rooms. When the desired temperature is reached, the roller shutter moves into the shade position. At dusk the roller shutters are closed, the heat remains in the rooms even in the absence of the occupants.
Roller shutters significantly improve thermal comfort.
A room is perceived as comfortable if the temperature differences between room air and different wall surfaces do not differ too much. In winter, however, the internal surface temperature of the window decreases. This cold surface extracts much more radiant heat than other wall surfaces (radiation asymmetry).
As a result, the residents feel unpleasant draughts. This discomfort is usually compensated for by an increase in room temperature. This increases the heating energy consumption considerably because in order to increase the room temperature by only one degree, one already needs 7% more energy.
Roller shutters are a tried and tested system of temporary heat protection
This is also confirmed by the Institut für Fenstertechnik e.V. from Rosenheim.
In winter and in the transitional periods, the most effective way to avoid energy losses at night is to use roller shutters.
During the day a large amount of free energy improves the energy balance by solar radiation through the windows.
More cost-intensive triple-glazed windows with a high thermal insulation value initially appear as an optimal solution, because heat losses can be reduced.
However, these do not offer the desired heating effect during the day, or only to a very limited extent, because the smaller the U-value, the more the g-value decreases.
It is not possible to optimize both characteristics (small U-value with large g-value) simultaneously
Therefore, who
- wants to reduce the heating capacity in winter
- does not want to do without the pleasant warmth of the sun's rays in the room
- wants to switch on the heating later during the transition times,
should pay attention to the g-value of the glazing.
Usually double insulating glass has a better solar heat yield because the energy transmittance (g-value) is higher and can therefore be used as a passive heating element.
The g value indicates how much energy from the solar radiation that hits the window enters the room (total energy transmission).
Example: At a g-value of 0.63 it is 63%.
The right decision is therefore:
- to install relatively inexpensive insulating windows in order to achieve the desired solar heating effect during the day
- to achieve high thermal insulation of windows with the help of roller shutters from the time of twilight
Also in summer the external sun protection is the most effective of all measures, because the heat is already absorbed in front of the glass.
This prevents the insulating glass from heating up and keeps the cool air inside.
The scientific study ESCO RP-EU25 proves that the reduction of the cooling energy requirement can exceed 80 % by means of an external shading device and that in certain temperate climatic zones an energy-absorbing air conditioning system is even completely superfluous.
- With internal sun protection too high temperatures can also occur in the gap due to the low rear ventilation in strong solar radiation, which can lead to glass breakage.
- Solar control glass has a light transmission of between 50 and 70 percent, but does not provide glare protection. "With windows facing south, sun protection glass can make sense," says Ulrich Tschorn, Managing Director of the Verband Fenster + Fassade (VFF). But one should be aware that this reduces the incidence of light in all seasons and in all weathers. The alternatives are external shading systems such as awnings, roller shutters or blinds.
- An external blind can be an annoying and expensive affair. Fully automatic systems often raise the external blinds even in the lightest wind or with a few drops of water, even when the sun is dazzling on the windows. The sensitivity of the automatic can be adjusted, but manufacturers and experienced homeowners recommend that the outside blind is raised once too often rather than once too little.
ROLLER SHUTTERS BLOCK 90% OF THE SUN'S ENERGY AND HAVE THE BEST ENERGY REDUCTION FACTOR (FC VALUE) OF ALL SUN PROTECTION IN COMBINATION WITH ALL WINDOWS
This is also confirmed by the Institut für Fenstertechnik e.V. from Rosenheim.
The Fc value describes the energy reduction factor of a sun protection device. The lower the value, the greater the reduction in solar radiation caused by the sun protection. The value 0.25 indicates that 25% of the solar energy can still penetrate into the interior.
At very high temperatures roller shutters can darken rooms that are not used at certain times of the day completely to keep the cool air inside.
Roller shutters in the rooms fend off solar radiation from the high summer sun by being partially closed.
The remaining light incidence can be regulated in the most modern way by an affordable interior blind.
With mirrored fins that can reflect the radiation, the unwanted rays can pass through the glass pane again without heating up the room. The view to the outside is maintained, repairs due to gusts of wind and weather influences are not to be feared with interior blinds.
In summer you can sleep with the window open
Who would like to sleep in the summer with open window secures itself by a roll shop which is so far closed that numerous light slots remain open, the permanent fresh air supply as well as a left night rest because by a secured roll shop the access is denied to the burglars.
Also in summer an automated control with sun and temperature sensors makes sense to achieve a maximum energy saving.
Thus all roller shutters are automatically raised and lowered according to the set times and the angle of incidence of the sun’s rays – even in the absence of the occupants.
The targeted use of combined sun protection and thermal insulation can save a small fortune per square metre of window and hour of sunshine in winter and summer.